共查询到18条相似文献,搜索用时 65 毫秒
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应用开发的微电导探针测试技术,对小尺寸颗粒玻璃珠(粒径分别为0.48、0.80、1.25 mm)和1.45 mm苯乙烯树脂为固相,空气和水分别为气相和液相的三相流化床的各相局部含率进行了同时测定.在较宽操作条件下,获得了一系列局部相含率实验数据.通过对实验数据研究发现:在充分发展段,局部固含率在r/R=0.75~0.85范围内有一个极大值,床层截面平均气含率随表观液速的变化存在一个极小值.在气体分布器区,在距气体分布器轴向一定距离范围内,三相局部含率的径向分布存在明显的不对称分布.随着轴向距离的增加,局部气含率径向不对称分布逐渐消失,最终过渡到对称分布,而局部固含率的径向不对称分布消失得不明显. 相似文献
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《化学工程》2015,(10):45-49
在以焦末为固相、空气为气相、水为液相的三相流化床中研究了局部气含率和局部固含率径向分布。实验用流化床内径100 mm,高1.7 m,焦末粒度1.07 mm。分别采用电导探针法和光纤法测定局部气含率和局部固含率。结果表明:表观气速为0.35—0.71 cm/s,表观液速为2.12—3.54 cm/s时,局部气含率在流化床中沿径向r/R=0—0.8处分布较均匀,在靠壁面处下降至约0.5%,且随表观液速增加而减小,随表观气速增加而增大,且在距分布板轴向高度分别为370 mm和470 mm时趋势一致,大小沿轴向增加,在表观气速一定时,液速小于2.12 cm/s时,气含率沿径向减小的趋势较明显。局部固含率沿径向分布较均匀,基本不随表观气速变化而变化,随表观液速增大而增大,且在距分布板轴向高度分别为370 mm和470 mm时趋势一致,大小沿轴向减小。 相似文献
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气液固三相循环流化床中气固相含率轴径向的分布 总被引:4,自引:0,他引:4
对气液固三相循环流化床中气固相含率沿轴径向的分布进行了实验研究和模拟。实验结果表明:与膨胀床相比,三相循环流化床内的相间接触较为充分;固含率轴向分布的一维沉降-扩散模型模拟值与实验值吻合较好。 相似文献
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在二维中试循环流化床中使用组合式固液分布器进行实验,考察下管箱表观液速,主分布器内径、主分布器下插深度,颗粒加入量和粒径对径向管束固含率的影响.结果表明:固含率随主分布器内径、颗粒加入量和下管箱表观液速的增加而增大,随粒径的增大而减小,随主分布器下插深度几乎没有变化;固含率不均匀度随颗粒粒径的增大而增大,随下管箱表观液速、颗粒加入量,主分布器下插深度增加而减小,但达到一定深度后,不均匀度不再随之减小,随主分布器内径几乎没有变化.在综合考虑各影响因素的基础上,提出计算固含率的经验公式,并用实验数据拟合了公式中的参数. 相似文献
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在一套新型液固提升管-流化床组合反应器中,以水-玻璃珠为液-固体系,对f500 mm′4000 mm的液固流化床反应器内不同高度颗粒固含率的径向分布进行了实验,考察了表观液速和颗粒循环速率操作条件对颗粒固含率径向分布的影响. 实验表明,液固流化床内流动区域在轴向上可以划分为分布器影响区、过渡区和均匀流化区,径向上可以划分为中心区和环隙区. 这种分布特征主要取决于分布器的结构、尺寸及其流化介质. 本工作还对液固流化床与气固喷动床的三区流动结构进行了比较. 相似文献
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气液固三相外环流反应器相含率分布与气液流动结构 总被引:1,自引:0,他引:1
结合电阻层析成像和差压法,以粒径3 mm的聚氨酯(密度1110 kg/m3)和粒径0.5, 1, 3 mm的玻璃珠(密度2460 kg/m3)为固相、空气为气相、水为液相,在直径0.09 m、高3.1 m的气液固三相气升式外环流反应器中考察了固相颗粒密度、粒径、固相含率对上升管和下降管中气含率的影响. 结果表明,当玻璃珠粒径为0.5和1 mm、表观气速ug>0.10 m/s时环流反应器可达到充分发展段. 以玻璃珠为固相时,气含率随固相含量和粒径增大而增大,从层析图像可见,在r/R=0~0.2处出现非导电相的极大值,且加入大颗粒的下降管中气固含率明显大于加入小颗粒的. 根据电阻层析成像的虚拟像,给出了时间序列的气固混合相的流动特征. 相似文献
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Axial and radial profiles of gas and solids holdups have been studied in agas-liquid-solid circulating fluidized bed at 140mm i.d..Experimental results indicate that the axialand radial profiles of gas and solids holdups are more uniform than those in a conventionalfluidized bed.Axial and radial liquid dispersion coefficients in the gas-liquid-solid circulating fluidizedbed are investigated for the first time.It is found that axial and radial liquid dispersioncoefficients increases with increaes in gas velocity and solids holdup.The liquid velocity has littleinfluence on the axial liquid dispersion coefficient,but would adversely affect the redial liquiddispersion coefficient.It can be concluded that the gas-liquid-solid circulating fluidized bed hasadvantages such as better interphase contact and lower liquid dispersion along the axial directionover the expanded bed. 相似文献
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气液固循环流化床颗粒分布板实验研究 总被引:8,自引:2,他引:8
设计了用于气液固三相循环流化床换热器的固体颗粒分布板。采用功能强大的CCD图像采集分析系统,获得颗粒的分布和运动规律,考察了安装高度、运行参数等对分布板颗粒分布性能的影响。研究表明,分布板的安装高度、液体和气体流量、颗粒体积分数等对颗粒的速度和固含率分布有较大影响,得到了使固体颗粒在管束中分布效果较好的设计参数,以指导工程应用。 相似文献
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汽液固三相循环流化床蒸发器已应用到盐化、烧碱、中药和造纸等工业中,表现出良好的防除垢性能。文中研究了这种新型流化床蒸发器的防、除垢机理。首先揭示出汽液固三相流剪应力对延长污垢的诱导期起主要作用,并对汽液固三相流剪应力和三相流剪应力增长率进行了定量计算,分析其影响因素。其次从污垢附着和剥蚀的角度,考察了固体颗粒的除垢作用。根据理论分析指出三相流剪应力对污垢附着需要的时间和污垢剥蚀比率的影响,从而计算了剥蚀比例和剥蚀速率及其影响因素。 相似文献
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S.A. Razzak 《Chemical engineering science》2007,62(24):7253-7263
Electrical resistance tomography (ERT) as an imaging technique was employed in this study for flow characterization, including simultaneous measurements of phase holdups and velocity distribution of individual phases in a gas-liquid-solid circulating fluidized Bed (GLSCFB). Application of ERT in three-phase flow systems is completely new. ERT is a non-invasive technique based on conductivity of the continuous phase, which provides color-coded cross-sectional view of the phases with a frequency of up to 250 Hz. The local conductivity measured by 16 electrodes located at the periphery of the plane inside the ERT measurement section, was then further converted into local phase concentration distribution based on Maxwell's relation. By cross-correlation analysis between the data obtained from both upstream and downstream planes, each consisting of eight electrodes, the phase propagation velocity was determined. Water was used as the continuous and conductive phase, while glass beads and air were non-conductive solid and gas phases, respectively. Qualitative and quantitative radial profiles of the phase holdup and propagation velocities were obtained. Phase holdup was also measured by pressure fluctuation, using online non-invasive pressure transducers and the results were in close agreement with the ERT results. 相似文献
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The influence of distributor structure on solids distribution is studied in two riser circulating fluidized bed reactors with different distributor structures but similar diameters. Optic fibre probes were used for the measurement of local solids distribution. The axial and radial distribution of solids holdup in the riser with a multi‐tube distributor is more uniform than that with a multi‐orifice distributor. The radial profiles of particle velocity in the riser with the multi‐tube distributor are also more uniform than that with the multi‐orifice distributor. In the riser with the multi‐tube distributor, both gas and particles are distributed more uniformly across the section, so that the flow acceleration is much more uniform and faster. The flow development is much faster and the fully developed region is reached early for the riser with the multi‐tube distributor. The distributor design is an important factor for the design of circulating fluidized bed reactor. 相似文献
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The hydrodynamics of a gas-liquid-solid circulating fluidized bed was investigated. A new regime, the three phase circulating fluidization regime, was discovered for the first time. The characteristics of this regime were compared with that of the conventional fluidization regime and the transport regime. The particle circulation rate and the gas and solids holdups in circulating fluidization regime were studied. 相似文献